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# For all positive integers m, [m]=3m when m is odd and [m]=

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Re: GMAT Prep, question 3 [#permalink]

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28 Sep 2009, 22:10
9 is odd: [9] = 3*9 = 27
6 is even: [6] = (1/2)*6 = 3

Hence [9] x [6] = 27 x 3 = 81
Ans: A

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Re: GMAT Prep, question 3 [#permalink]

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28 Sep 2009, 22:28
yangsta8 wrote:
9 is odd: [9] = 3*9 = 27
6 is even: [6] = (1/2)*6 = 3

Hence [9] x [6] = 27 x 3 = 81
Ans: A

My bad. The answers should have been worded as follows (which makes a difference).

A. [81]

B. [54]

C. [36]

D. [27]

E. [18]

When the answers are reworded, the correct answer is D, or [27]. It looks like GMAC was tricky with this question and some readers didn't notice the answers were surrounded by a box. Fortunately, I was lucky enough to find a thread that discusses this:

gmatprep-question-82890.html#p621771

Looks like I wasn't the only one that was tricked, lol.

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Re: GMAT Prep, question 3 [#permalink]

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29 Sep 2009, 11:51
agree with gmattester123, good catch!.

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07 Oct 2009, 12:37
For all positive integers m,[m]=3m when m is odd and [m]=1/2m when m is even.which of the following is equivalent to [9]*[6]?
A)[81]
B)[54]
C)[36]
D)[27]
E)[18]

can anybody answer this with explanation.

Thanks

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07 Oct 2009, 14:43
yogitapruthi wrote:
For all positive integers m,[m]=3m when m is odd and [m]=1/2m when m is even.which of the following is equivalent to [9]*[6]?
A)[81]
B)[54]
C)[36]
D)[27]
E)[18]

can anybody answer this with explanation.

Thanks

[9] = 3 x 9 = 27
[6] = 6/2 = 3

so [9].[6]= 27 x 3 = [27] (as 27 is odd)
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07 Oct 2009, 21:13
 ! Please post PS questions in the PS subforum: gmat-problem-solving-ps-140/Please post DS questions in the DS subforum: gmat-data-sufficiency-ds-141/No posting of PS/DS questions is allowed in the main Math forum.

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08 Oct 2009, 03:17
Ans is OA D [27]
here one thing to notice is [] is a function or operator...you have to use it in your option choice

[9] = 3 x 9 = 27
[6] = 6/2 = 3
[9]*[6] = 27*3 = 81

A) [81] = 81 x 3 = 343
B) [54] = 1/2 x 54 = 27
C) [36] = 1/2 x 36 = 18
D) [27] = 3 x 27 = 81

Hence OA D is our ans
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Seemingly easy PS question! Help! [#permalink]

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29 Dec 2009, 18:57
hi guys,
I can't figure out why I can't get this question right, appreciate all comments in advance.

Q: For all positive integers m, [m]=3m when m is odd and [m]=1/2 m when m is even. What is [9] x [6] equivalent to?

1) [81]
2) [18]
3) [27]
4) [54]
5) [36]

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Re: Seemingly easy PS question! Help! [#permalink]

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29 Dec 2009, 20:40
Funny, I came across this questions today as well and I answered it the same way. It's not that 81 is wrong, it's that we chose the wrong answer. I think the asterisk represents a box, right? All of the answer choices were boxed, therefore we're still supposed to follow the rules mentioned in the question. 27* is right because 27 multiplied by 3 (the rule for odd integers) is 81.

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Re: Seemingly easy PS question! Help! [#permalink]

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29 Dec 2009, 20:59
The asterisk is a box! But I couldn't copy and paste so I had to come up with something
Oh God, now I got it. You're soo right! I completely ignored the fact that the answers were in the box too. My bad. Thanks a lot!
Did you look at my other post too? I have a feeling I'm ignoring something obvious in that one too!
Thanks again!

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06 Jan 2010, 04:44
Attachments

untitled.JPG [ 53.57 KiB | Viewed 1412 times ]

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Re: Strange GMAT Prep Question [#permalink]

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06 Jan 2010, 05:07
[9] = 3*9=27

[6] = 6/2 = 3

[9] * [6] = 81

It is equivalent to [27] = 3*27 = 81

It is not [81] = 3 * 81 = 243

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Re: Strange GMAT Prep Question [#permalink]

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06 Jan 2010, 05:08
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Expert's post
81 is correct as the total but if u have to get an ans inside a sq the total is 3 times what is in the box.....
so 81/3 is the ans...
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Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

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Re: Strange GMAT Prep Question [#permalink]

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06 Jan 2010, 05:28
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Thanks Guys ..!! Such a silly mistake from my side ,it costed me 51 in GPREP..!!

I got 5 total wrong and this being one of them

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Re: Seemingly easy PS question! Help! [#permalink]

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11 Jan 2010, 18:24
Parisa1362 wrote:
hi guys,
I can't figure out why I can't get this question right, appreciate all comments in advance.

Q: For all positive integers m, [m]=3m when m is odd and [m]=1/2 m when m is even. What is [9] x [6] equivalent to?

1) [81]
2) [18]
3) [27]
4) [54]
5) [36]

Because [m] = 3m when m is odd, [9]=3m, m=3. Using the same logic for [6], [6]=3
3*3=9
If you put this back in [m] form you get 3*9=[27] (we must use 3m because m is odd, if it were even it would be .5*9)

Also, you can confirm this by [27]=3m, m=9

Does that help?

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Re: Seemingly easy PS question! Help! [#permalink]

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11 Jan 2010, 19:10
Another way of looking at this is as follows:
[9] x [6] = ?

[9] = 3(9) = 27
[6] = 0.5(6) = 3
Therefore, [9]x[6] = 27x3 = 81

We need a [x] that equals to 81. Only [27]=3(27)=81. Therefore the answer is C) [27].

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Tough Algebra, Can anyone help me? Thanks!! [#permalink]

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08 Feb 2010, 15:20
Attachment:

Presentation1.jpg [ 26.15 KiB | Viewed 4036 times ]

[Reveal] Spoiler:
Thanks for the help.
It's from GMAT Prep, my answer is 81, but OA is 27. Anyone knows how to get the right answer?
Thank you so much again for the great help and time!!

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Re: Tough Algebra, Can anyone help me? Thanks!! [#permalink]

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08 Feb 2010, 15:52
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Expert's post
We know that [9] = 3*9 = 27, since [x] = 3x when x is odd. We also know that [6] = 3, since [x] = x/2 when x is even. So [9]*[6] = 27*3 = 81.

Now, many people choose the wrong answer to this question, despite doing all of the work correctly, because they do not notice that the answer choices are all in boxes - a devious GMAT trap. So the answer choice which reads [81] is not equal to the number 81; it is equal to 3*81 = 243, because [x] = 3x when x is odd. The correct answer here is [27], which is equal to the number 81.
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Re: Tough Algebra, Can anyone help me? Thanks!! [#permalink]

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09 Feb 2010, 01:05
note the answers given are in box

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Re: Tough Algebra, Can anyone help me? Thanks!! [#permalink]

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09 Feb 2010, 04:53
Since the numbers are in boxes, we have to solve the Question twice.

First look at the given numbers (9 is odd so 3m, 6 is even so 1/2m)
[9]x[6] = 3(9)x1/2(6) = 81

Now look at 81 which is obviously odd which means that the answer has to be 3m = 81 (answer is also in a box)

hence, m = [27]

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Re: Tough Algebra, Can anyone help me? Thanks!!   [#permalink] 09 Feb 2010, 04:53

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